Doped graphene electronic materials

ABSTRACT

A graphene substrate is doped with one or more functional groups to form an electronic device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to and claims the benefit of theearliest available effective filing date(s) from the following listedapplication(s) (the “Related Applications”) (e.g., claims earliestavailable priority dates for other than provisional patent applicationsor claims benefits under 35 USC §119(e) for provisional patentapplications, for any and all parent, grandparent, great-grandparent,etc. applications of the Related Application(s)). All subject matter ofthe Related Applications and of any and all parent, grandparent,great-grandparent, etc. applications of the Related Applications isincorporated herein by reference to the extent such subject matter isnot inconsistent herewith.

RELATED APPLICATIONS

For purposes of the USPTO extra-statutory requirements, the presentapplication constitutes a continuation-in-part of U.S. patentapplication Ser. No. 12/658,168, entitled DOPED GRAPHENE ELECTRONICMATERIALS, naming Jeffrey A. Bowers, Roderick A. Hyde, Muriel Y.Ishikawa, Jordin T. Kare, Clarence T. Tegreene, Tatsushi Toyokuni andRichard N. Zare as inventors, filed 2 Feb. 2010, which is currentlyco-pending, or is an application of which a currently co-pendingapplication is entitled to the benefit of the filing date.

The United States Patent Office (USPTO) has published a notice to theeffect that the USPTO's computer programs require that patent applicantsreference both a serial number and indicate whether an application is acontinuation or continuation-in-part. Stephen G. Kunin, Benefit ofPrior-Filed Application, USPTO Official Gazette Mar. 18, 2003, availableat http://www.uspto.gov/web/offices/com/sol/og/2003/week 11/patbene.htm.The present Applicant Entity (hereinafter “Applicant”) has providedabove a specific reference to the application(s)from which priority isbeing claimed as recited by statute. Applicant understands that thestatute is unambiguous in its specific reference language and does notrequire either a serial number or any characterization, such as“continuation” or “continuation-in-part,” for claiming priority to U.S.patent applications. Notwithstanding the foregoing, Applicantunderstands that the USPTO's computer programs have certain data entryrequirements, and hence Applicant is designating the present applicationas a continuation-in-part of its parent applications as set forth above,but expressly points out that such designations are not to be construedin any way as any type of commentary and/or admission as to whether ornot the present application contains any new matter in addition to thematter of its parent application(s).

SUMMARY

In one aspect, an electronic device includes a graphene substrateincluding a first defined region and a second defined region differingin at least one electronic property (e.g., Fermi level, band structure,carrier populations, mobility, tunneling behavior, or conductivecharacter) from the first defined region. The first defined region ischemically functionalized with a first dopant species and the seconddefined region is chemically functionalized with a second dopantspecies.

The difference in the at least one electronic property may be aconsequence of the functionalization. The first and second definedregions may form a semiconducting junction, and may be parts of acomponent such as a diode, a transistor, a switch, a resistor, acapacitor, an inductor, a sensor, or an interconnect. The device mayfurther include interconnects electrically connected to the first andsecond defined regions. The graphene substrate may include a singlelayer or a multilayer. The first and second regions may be adjacent, andeither or both may be remote from an edge of the graphene substrate. Thedevice may further include a third defined region differing in at leastone electronic property from the first and second defined regions, whichmay be functionalized with a third dopant species. The graphenesubstrate may be disposed on a base substrate (e.g., graphite or acrystal containing a noncarbon component). The first and second dopantspecies may functionalize a common surface of the substrate or opposingsurfaces, and either or both may include an amine, an imine, an organicfree radical, an aromatic molecule, nitrogen, boron, gold, bismuth,antimony, bromine, iodine, a diazonium salt, hydrogen, or an alkylgroup, and may be different or the same. The first and second dopantspecies may differ in concentration, attachment pattern to the graphenesubstrate, or number density.

Either or both dopant species may include a plurality of intermixeddopant subspecies, which may include the same or different subspecies,and which may differ in attachment pattern or relative concentrationfrom one another. One or more dopant subspecies may vary inconcentration within the first defined region. The first dopant speciesmay include a first bound moiety affixed to the graphene substrate and afirst free moiety removably attached to the first bound moiety, in whichcase the difference in the electronic property may be a function of aproperty of the free moiety. The second dopant species may include asecond bound moiety affixed to the graphene substrate and a second freemoiety removably attached to the second bound moiety, in which case thefirst and second bound moieties may be the same or different. The firstdopant species may be adsorbed onto the graphene substrate (e.g.,chemisorbed or physisorbed), chemically bound to the substrate (e.g.,covalently bound), or intercalated in the graphene substrate. The firstdopant species may vary in concentration or attachment pattern withinthe first defined region. The second defined region may surround thefirst defined region.

In another aspect, an electronic device includes a graphene substrateincluding a first defined region and a second defined region differingin at least one electronic property (e.g., Fermi level, band structure,carrier populations, mobility, tunneling behavior, or conductivecharacter) from the first defined region. The first region is chemicallyfunctionalized with a first dopant species and is remote from any edgeof the graphene substrate.

The second defined region may be chemically functionalized with a seconddopant species, which may differ from the first dopant species. Thefirst and second dopant species may differ in concentration, attachmentpattern on the graphene substrate, or number density. Either or bothdopant species may include a plurality of intermixed dopant subspecies,which may include the same or different subspecies, and which may differin attachment pattern or relative concentration from one another. One ormore dopant subspecies may vary in concentration within the firstdefined region. The first and second dopant species may functionalize acommon surface of the substrate or opposing surfaces, and either or bothmay include an amine, an imine, an organic free radical, an aromaticmolecule, nitrogen, boron, gold, bismuth, antimony, bromine, iodine, adiazonium salt, hydrogen, or an alkyl group, and may be different or thesame.

The difference in the at least one electronic property may be aconsequence of the functionalization. The first and second definedregions may form a semiconducting junction, and may be parts of acomponent such as a diode, a transistor, a switch, a resistor, acapacitor, an inductor, a sensor, or an interconnect. The device mayfurther include interconnects electrically connected to the first andsecond defined regions. The graphene substrate may include a singlelayer or a multilayer. The first and second regions may be adjacent, andeither or both may be remote from an edge of the graphene substrate. Thedevice may further include a third defined region differing in at leastone electronic property from the first and second defined regions, whichmay be functionalized with a third dopant species. The graphenesubstrate may be disposed on a base substrate (e.g., graphite or acrystal containing a noncarbon component). The first dopant species mayinclude a first bound moiety affixed to the graphene substrate and afirst free moiety removably attached to the first bound moiety, in whichcase the difference in the electronic property may be a function of aproperty of the free moiety. The second defined region may be chemicallyfunctionalized with a second dopant species including a second boundmoiety affixed to the graphene substrate and a second free moietyremovably attached to the second bound moiety, in which case thecomposition of the first and second bound moieties may be the same ordifferent. The first dopant species may be adsorbed onto the graphenesubstrate (e.g., chemisorbed or physisorbed), chemically bound to thesubstrate (e.g., covalently bound), or intercalated in the graphenesubstrate. The first dopant species may vary in concentration orattachment pattern within the first defined region. The second definedregion may surround the first defined region.

In another aspect, an electronic circuit includes a graphene substrateincluding a first device and a second device. The first device includesa first defined region and a second defined region differing in at leastone first electronic property (e.g., Fermi level, band structure,carrier populations, mobility, tunneling behavior, or conductivecharacter) from the first defined region, wherein the first region ischemically functionalized with a first dopant species. The second deviceincludes a third defined region and a fourth defined region differing inat least one second electronic property (e.g., Fermi level, bandstructure, carrier populations, mobility, tunneling behavior, orconductive character) from the third defined region, wherein the thirdregion is chemically functionalized with a second dopant species.

The first and second dopant species may be the same or different. Thefirst and second devices have substantially the same electroniccharacter. The circuit may further include a fifth defined region of thegraphene substrate that functions as an interconnect between the firstand second devices. The at least one first electronic property and theat least one second electronic property may include a common electronicproperty. The difference in the at least one first electronic propertymay be a consequence of the functionalization of the first and seconddefined regions, or the difference in the at least one second electronicproperty may be a consequence of the functionalization of the third andfourth defined regions. The first and second defined regions, or thethird and fourth defined regions, may form a semiconducting junction.The first or second device may be a diode, a transistor, a switch, aresistor, a capacitor, an inductor, a sensor, or an interconnect.

The graphene substrate may include a single layer or a multilayer. Thefirst defined region and the second defined region, or the third definedregion and the fourth defined region, may be adjacent. The first orsecond defined region may not include an edge of the graphene substrate.The graphene substrate may be disposed on a base substrate (e.g.,graphite or a crystal containing a noncarbon component). The firstdopant species and the second dopant species may functionalize a commonsurface of the graphene substrate or opposing surfaces, and the firstdevice and the second device may be positioned on opposing surfaces ofthe graphene substrate. The first or second dopant species may includeat least one of an amine, an imine, an organic free radical, an aromaticmolecule, nitrogen, boron, gold, bismuth, antimony, bromine, iodine, adiazonium salt, hydrogen, or an alkyl group.

The second dopant species may differ from the first dopant species. Thefirst and second dopant species may differ in concentration, attachmentpattern to the graphene substrate, or number density. Any of the dopantspecies may include a plurality of intermixed dopant subspecies, whichmay include the same or different subspecies, and which may differ inattachment pattern or relative concentration from one another. One ormore dopant subspecies may vary in concentration within the firstdefined region. The first dopant species may include a first boundmoiety affixed to the graphene substrate and a first free moietyremovably attached to the first bound moiety, in which case thedifference in the electronic property may be a function of a property ofthe free moiety. The second dopant species may include a second boundmoiety affixed to the graphene substrate and a second free moietyremovably attached to the second bound moiety, in which case the firstand second bound moieties may be the same or different. The first dopantspecies may be adsorbed onto the graphene substrate (e.g., chemisorbedor physisorbed), chemically bound to the substrate (e.g., covalentlybound), or intercalated in the graphene substrate. The first dopantspecies may vary in concentration or attachment pattern within the firstdefined region. The second defined region may surround the first definedregion.

In another aspect, a method of forming an electronic device on agraphene substrate includes functionalizing a first defined region ofthe graphene substrate with a first dopant species, and functionalizinga second defined region of the graphene substrate with a second dopantspecies. The functionalized first region differs in an electricalproperty (e.g., Fermi level, band structure, carrier populations,mobility, tunneling behavior, or conductive character) from thefunctionalized second defined region.

Functionalizing the first defined region may include selectivelyexposing the first region to a chemical solution, lithographicallymasking the graphene substrate, applying a spatially patternedelectrical potential to the graphene substrate, or introducing a defectinto the graphene substrate. The first defined region and the seconddefined region may be functionalized simultaneously, or the firstdefined region may be functionalized before the second defined region.The second defined region may overlap the first defined region.Functionalizing the second defined region may include co-depositing thesecond dopant species with the first dopant species. The first dopantspecies may exclude the second dopant species from depositing on thegraphene substrate. The second defined region may surround the firstdefined region, or the first defined region may surround the seconddefined region.

In another aspect, a method of forming an electronic device on agraphene substrate includes functionalizing a first defined region ofthe graphene substrate with a first dopant species. The functionalizedfirst region differs in an electrical property (e.g., Fermi level, bandstructure, carrier populations, mobility, tunneling behavior, orconductive character) from a second defined region (which may or may notbe functionalized) and is remote from any edge of the graphenesubstrate.

Functionalizing the first defined region may include selectivelyexposing the first region to a chemical solution, lithographicallymasking the graphene substrate, applying a spatially patternedelectrical potential to the graphene substrate, or introducing a defectinto the graphene substrate. The first defined region and the seconddefined region may be functionalized simultaneously, or the firstdefined region may be functionalized before the second defined region.The second defined region may overlap the first defined region.Functionalizing the second defined region may include co-depositing thesecond dopant species with the first dopant species. The first dopantspecies may exclude the second dopant species from depositing on thegraphene substrate. The second defined region may surround the firstdefined region, or the first defined region may surround the seconddefined region.

In another aspect, an optoelectronic device includes a graphenesubstrate including a first defined region and a second defined regiondiffering in at least one electro-optical property (e.g., optical gain,transmissivity, reflectivity, permittivity, permeability, refractiveindex, or anisotropy) from the first defined region. The first region ischemically functionalized with a first dopant species and the seconddefined region is chemically functionalized with a second dopantspecies.

The difference in the at least one electro-optical property may be aconsequence of the functionalization. The first and second definedregions may be parts of a component such as laser, a light-emittingdiode, a plasmon waveguide, an optical waveguide, an optical grating, afluorescent device, a light-absorbing device, a photoelectron converter,a phaseshifting device, a interferometer, an optical coupler, or aplasmon coupler, and the optoelectronic device may be nonlinear or be aplasmonic device. The device may further include interconnects opticallyconnected to the first and second defined regions. The graphenesubstrate may include a single layer or a multilayer. The graphenesubstrate may be disposed on a base substrate (e.g., graphite or acrystal containing a noncarbon component). The first and second dopantspecies may functionalize a common surface of the substrate or opposingsurfaces, and either or both may include an amine, an imine, an organicfree radical, an aromatic molecule, nitrogen, boron, gold, bismuth,antimony, bromine, iodine, a diazonium salt, hydrogen, or an alkylgroup, and may be different or the same. The first and second dopantspecies may differ in concentration, attachment pattern to the graphenesubstrate, or number density.

The first dopant species may include a first bound moiety affixed to thegraphene substrate and a first free moiety removably attached to thefirst bound moiety, in which case the difference in the electro-opticalproperty may be a function of a property of the free moiety. The seconddopant species may include a second bound moiety affixed to the graphenesubstrate and a second free moiety removably attached to the secondbound moiety, in which case the first and second bound moieties may bethe same or different. The first dopant species may be adsorbed onto thegraphene substrate (e.g., chemisorbed or physisorbed), chemically boundto the substrate (e.g., covalently bound), or intercalated in thegraphene substrate. The first dopant species may vary in concentrationor attachment pattern within the first defined region. The seconddefined region may surround the first defined region.

In another aspect, an optoelectronic device includes a graphenesubstrate including a first defined region and a second defined regiondiffering in at least one electro-optical property (e.g., optical gain,transmissivity, reflectivity, permittivity, permeability, refractiveindex, or anisotropy) from the first defined region. The first region ischemically functionalized with a first dopant species and does notinclude an edge of the graphene substrate.

The second defined region may be chemically functionalized with a seconddopant species, which may differ from the first dopant species. Thefirst and second dopant species may differ in concentration, attachmentpattern on the graphene substrate, or number density. The first dopantspecies may include a first bound moiety affixed to the graphenesubstrate and a first free moiety removably attached to the first boundmoiety, in which case the difference in the electro-optical property maybe a function of a property of the free moiety. The second definedregion may be chemically functionalized with a second dopant speciesincluding a second bound moiety affixed to the graphene substrate and asecond free moiety removably attached to the second bound moiety, inwhich case the composition of the first and second bound moieties may bethe same or different. The optoelectronic device may include a laser, alight-emitting diode, a plasmon waveguide, an optical waveguide, anoptical grating, a fluorescent device, a light-absorbing device, aphotoelectron converter, a phaseshifting device, a interferometer, anoptical coupler, or a plasmon coupler, and the optoelectronic device maybe nonlinear or be a plasmonic device. The difference in the at leastone electro-optical property may be a consequence of thefunctionalization. The device may further include interconnectsoptically connected to the first and second defined regions. Thegraphene substrate may include a single layer or a multilayer. Thegraphene substrate may be disposed on a base substrate (e.g., graphiteor a crystal containing a noncarbon component). The first and seconddopant species may functionalize a common surface of the substrate oropposing surfaces, and either or both may include an amine, an imine, anorganic free radical, an aromatic molecule, nitrogen, boron, gold,bismuth, antimony, bromine, iodine, a diazonium salt, hydrogen, or analkyl group, and may be different or the same. The first dopant speciesmay be adsorbed onto the graphene substrate (e.g., chemisorbed orphysisorbed), chemically bound to the substrate (e.g., covalentlybound), or intercalated in the graphene substrate. The first dopantspecies may vary in concentration or attachment pattern within the firstdefined region. The second defined region may surround the first definedregion.

In another aspect, an optoelectronic circuit includes a graphenesubstrate including a first device and a second device. The first deviceincludes a first defined region and a second defined region differing inat least one first electro-optical property (e.g., optical gain,transmissivity, reflectivity, permittivity, permeability, refractiveindex, or anisotropy) from the first defined region, wherein the firstregion is chemically functionalized with a first dopant species. Thesecond device includes a third defined region and a fourth definedregion differing in at least one second electro-optical property (e.g.,optical gain, transmissivity, reflectivity, permittivity, permeability,refractive index, or anisotropy) from the third defined region, whereinthe third region is chemically functionalized with a second dopantspecies.

The first and second dopant species may be the same or different. Thefirst and second devices have substantially the same electro-opticalcharacter. The circuit may further include a fifth defined region of thegraphene substrate that functions as an optical interconnect between thefirst and second devices. The at least one first electro-opticalproperty and the at least one second electro-optical property mayinclude a common electro-optical property. The difference in the atleast one first electro-optical property may be a consequence of thefunctionalization of the first and second defined regions, or thedifference in the at least one second electro-optical property may be aconsequence of the functionalization of the third and fourth definedregions. The first or second device may be a laser, a light-emittingdiode, a plasmon waveguide, an optical waveguide, an optical grating, afluorescent device, a light-absorbing device, a photoelectron converter,a phaseshifting device, a interferometer, an optical coupler, or aplasmon coupler.

The graphene substrate may include a single layer or a multilayer. Thefirst defined region and the second defined region, or the third definedregion and the fourth defined region, may be adjacent. The first orsecond defined region may not include an edge of the graphene substrate.The graphene substrate may be disposed on a base substrate (e.g.,graphite or a crystal containing a noncarbon component). The firstdopant species and the second dopant species may functionalize a commonsurface of the graphene substrate or opposing surfaces, and the firstdevice and the second device may be positioned on opposing surfaces ofthe graphene substrate. The first or second dopant species may includeat least one of an amine, an imine, an organic free radical, an aromaticmolecule, nitrogen, boron, gold, bismuth, antimony, bromine, iodine, adiazonium salt, hydrogen, or an alkyl group.

The second dopant species may differ from the first dopant species. Thefirst and second dopant species may differ in concentration, attachmentpattern to the graphene substrate, or number density. Any of the dopantspecies may include a plurality of intermixed dopant subspecies, whichmay include the same or different subspecies, and which may differ inattachment pattern or relative concentration from one another. One ormore dopant subspecies may vary in concentration within the firstdefined region. The first dopant species may include a first boundmoiety affixed to the graphene substrate and a first free moietyremovably attached to the first bound moiety, in which case thedifference in the electro-optical property may be a function of aproperty of the free moiety. The second dopant species may include asecond bound moiety affixed to the graphene substrate and a second freemoiety removably attached to the second bound moiety, in which case thefirst and second bound moieties may be the same or different. The firstdopant species may be adsorbed onto the graphene substrate (e.g.,chemisorbed or physisorbed), chemically bound to the substrate (e.g.,covalently bound), or intercalated in the graphene substrate. The firstdopant species may vary in concentration or attachment pattern withinthe first defined region. The second defined region may surround thefirst defined region.

In another aspect, a method of forming an optoelectronic device on agraphene substrate includes functionalizing a first defined region ofthe graphene substrate with a first dopant species, and functionalizinga second defined region of the graphene substrate with a second dopantspecies. The functionalized first region differs in an electro-opticalproperty (e.g., optical gain, transmissivity, reflectivity,permittivity, permeability, refractive index, or anisotropy) from thefunctionalized second defined region.

The first dopant species and the second dopant species may be selectedto confer a first electro-optical property and a second electro-opticalproperty on the first defined region and second defined region,respectively. Functionalizing the first defined region may includeselectively exposing the first region to a chemical solution,lithographically masking the graphene substrate, or applying a spatiallypatterned electrical potential to the graphene substrate.

In another aspect, a method of forming an optoelectronic device on agraphene substrate includes functionalizing a first defined region ofthe graphene substrate with a first dopant species. The functionalizedfirst region differs in an electro-optical property (e.g., optical gain,transmissivity, reflectivity, permittivity, permeability, refractiveindex, or anisotropy) from a second defined region and is remote fromany edge of the graphene substrate.

The first dopant species may be selected to confer a firstelectro-optical property on the first defined region. Functionalizingthe first defined region may include selectively exposing the firstregion to a chemical solution, lithographically masking the graphenesubstrate, or applying a spatially patterned electrical potential to thegraphene substrate.

In another aspect, an electronic device includes a graphene substrateincluding a junction between an n-type defined region and a p-typedefined region. The n-type region is chemically functionalized with afirst dopant species and the p-type defined region is chemicallyfunctionalized with a second dopant species.

The graphene substrate may further include a neutral region (e.g., aninsulator, a semiconductor, or a metal) having substantially fewer freecarriers than either the n-type defined region or the p-type definedregion. The n-type and p-type defined regions may be parts of acomponent such as a diode, a transistor, a switch, a resistor, acapacitor, an inductor, a sensor, or an interconnect. The device mayfurther include interconnects electrically connected to the n-type andp-type defined regions. The graphene substrate may include a singlelayer or a multilayer. Either or both of the n-type and p-type regionsmay be remote from an edge of the graphene substrate. The device mayfurther include a third defined region differing in at least oneelectronic property from the n-type and p-type defined regions, whichmay be functionalized with a third dopant species.

The graphene substrate may be disposed on a base substrate (e.g.,graphite or a crystal containing a noncarbon component). The first andsecond dopant species may functionalize a common surface of thesubstrate or opposing surfaces, and may be the same or different. Thefirst dopant species may include at least one of an amine, an imine, anorganic free radical, or an aromatic molecule, and the second dopantspecies may include at least one of an aromatic molecule, boron, gold,bismuth, antimony, bromine, iodine, a diazonium salt, hydrogen, and analkyl group. The first and second dopant species may differ inconcentration, attachment pattern to the graphene substrate, or numberdensity.

Either or both dopant species may include a plurality of intermixeddopant subspecies, which may include the same or different subspecies,and which may differ in attachment pattern or relative concentrationfrom one another. One or more dopant subspecies may vary inconcentration within the n-type or p-type defined region. The firstdopant species may include a first bound moiety affixed to the graphenesubstrate and a first free moiety removably attached to the first boundmoiety, in which case the difference in the electronic property (e.g.,free carrier population) may be a function of a property of the freemoiety. The second dopant species may include a second bound moietyaffixed to the graphene substrate and a second free moiety removablyattached to the second bound moiety, in which case the first and secondbound moieties may be the same or different. The first or second dopantspecies may be adsorbed onto the graphene substrate (e.g., chemisorbedor physisorbed), chemically bound to the substrate (e.g., covalentlybound), or intercalated in the graphene substrate. The first or seconddopant species may vary in concentration or attachment pattern withinthe n-type or p-type defined region. The p-type defined region maysurround the n-type defined region, or the n-type defined region maysurround the p-type defined region.

In another aspect, an electronic device includes a graphene substrateincluding a first defined region chemically functionalized with a firstdopant species. The first dopant species has a concentration that variesacross the first defined region (e.g., stepwise across the definedregion or smoothly across the defined region).

The device may have at least one electronic property (e.g., Fermi level,band structure, carrier populations, mobility, tunneling behavior, orconductive character) that varies across the first defined region, forexample as a consequence of the functionalization of the first definedregion. The first region may be part of a component such as a diode, atransistor, a switch, a resistor, a capacitor, an inductor, a sensor, oran interconnect. The device may further include an interconnectelectrically connected to the first defined region. The graphenesubstrate may include a single layer or a multilayer. The first regionmay be remote from an edge of the graphene substrate. The graphenesubstrate may be disposed on a base substrate (e.g., graphite or acrystal containing a noncarbon component). The first dopant species mayinclude an amine, an imine, an organic free radical, an aromaticmolecule, nitrogen, boron, gold, bismuth, antimony, bromine, iodine, adiazonium salt, hydrogen, or an alkyl group, and may vary in attachmentpattern to the graphene substrate.

The first dopant species may include a plurality of intermixed dopantsubspecies. One or more dopant subspecies may vary in concentrationwithin the first defined region. The first dopant species may include afirst bound moiety affixed to the graphene substrate and a first freemoiety removably attached to the first bound moiety, in which case thedifference in the electronic property may be a function of a property ofthe free moiety. The first dopant species may be adsorbed onto thegraphene substrate (e.g., chemisorbed or physisorbed), chemically boundto the substrate (e.g., covalently bound), or intercalated in thegraphene substrate.

In another aspect, an electronic circuit includes a first device and asecond device. The first device includes a first junction between afirst n-type defined region and a first p-type defined region, whereinthe first n-type region is chemically functionalized with a first dopantspecies and the first p-type defined region is chemically functionalizedwith a second dopant species. The second device includes a secondjunction between a second n-type defined region and a second p-typedefined region, wherein the n-type region is chemically functionalizedwith a third dopant species and the p-type defined region is chemicallyfunctionalized with a fourth dopant species.

The first and third dopant species, or the second and fourth dopantspecies, may be the same, and the first and second devices may havesubstantially the same electronic character. The circuit may furtherinclude a fifth defined region of the graphene substrate that functionsas an interconnect between the first and second devices. The first orsecond device may be a diode, a transistor, a switch, a resistor, acapacitor, an inductor, a sensor, or an interconnect. The graphenesubstrate may include a single layer or a multilayer.

The first n-type or first p-type defined region may not include an edgeof the graphene substrate. The graphene substrate may be disposed on abase substrate (e.g., graphite or a crystal containing a noncarboncomponent). The first dopant species and the second dopant species mayfunctionalize a common surface of the graphene substrate or opposingsurfaces, and the first device and the second device may be positionedon opposing surfaces of the graphene substrate. The first dopant speciesmay include at least one of an amine, an imine, an organic free radical,or an aromatic molecule, and the second dopant species may include atleast one of an aromatic molecule, boron, gold, bismuth, antimony,bromine, iodine, a diazonium salt, hydrogen, or an alkyl group.

The second dopant species may differ from the first dopant species. Thefirst and second dopant species may differ in concentration, attachmentpattern to the graphene substrate, or number density. Any of the dopantspecies may include a plurality of intermixed dopant subspecies, whichmay include the same or different subspecies, and which may differ inattachment pattern or relative concentration from one another. One ormore dopant subspecies may vary in concentration within the firstdefined region. The first dopant species may include a first boundmoiety affixed to the graphene substrate and a first free moietyremovably attached to the first bound moiety, in which case thedifference in the electronic property may be a function of a property ofthe free moiety. The second dopant species may include a second boundmoiety affixed to the graphene substrate and a second free moietyremovably attached to the second bound moiety, in which case the firstand second bound moieties may be the same or different. The first orsecond dopant species may be adsorbed onto the graphene substrate (e.g.,chemisorbed or physisorbed), chemically bound to the substrate (e.g.,covalently bound), or intercalated in the graphene substrate. The firstor second dopant species may vary in concentration or attachment patternwithin the first n-type or p-type defined region, respectively. Thefirst p-type defined region may surround the first n-type definedregion, or the first n-type defined region may surround the first p-typedefined region.

In another aspect, a method of forming an electronic device on agraphene substrate includes functionalizing a first defined region ofthe graphene substrate with a first dopant species selected to confer ann-type character on the first defined region, and functionalizing asecond defined region of the graphene substrate with a second dopantspecies selected to confer a p-type character on the second definedregion.

Functionalizing the first or second defined region may includeselectively exposing the first defined region to a chemical solution,lithographically masking the graphene substrate, applying a spatiallypatterned electrical potential to the graphene substrate, or introducinga defect into the graphene substrate. The first defined region and thesecond defined region may be functionalized simultaneously orsequentially. The second defined region may overlap the first definedregion. Functionalizing the first or second defined region may includeco-depositing the second dopant species with the first dopant species.Either or both of the dopant species may exclude the other fromdepositing on the graphene substrate. The second defined region maysurround the first defined region, or the first defined region maysurround the second defined region.

In another aspect, an electronic device includes a graphene substrateincluding a first defined region and a second defined region differingin at least one electronic property (e.g., Fermi level, band structure,carrier populations, mobility, tunneling behavior, or conductivecharacter) from the first defined region. The first region is chemicallyfunctionalized with a first dopant species on a first surface of thegraphene substrate, and the second region is chemically functionalizedwith a second dopant species on a second surface of the graphenesubstrate. The second surface opposes the first surface.

The first region may be chemically functionalized on opposing surfacesof the graphene substrate. The difference in the at least one electronicproperty may be a consequence of the functionalization of the first andsecond defined regions. The first and second defined regions may form asemiconducting junction, and may be parts of a component such as adiode, a transistor, a switch, a resistor, a capacitor, an inductor, asensor, or an interconnect. The device may further include a firstinterconnect electrically connected to the first defined region and asecond interconnect electrically connected to the second defined region.The graphene substrate may include a single layer or a multilayer. Thefirst defined region and the second defined region may be adjacent, andeither may not include an edge of the graphene substrate. The device mayfurther include a third defined region differing in at least oneelectronic property from each of the first defined region and the seconddefined region. The third defined region may be chemicallyfunctionalized with a third dopant species. The first or second dopantspecies may includes at least one of an amine, an imine, an organic freeradical, an aromatic molecule, nitrogen, boron, gold, bismuth, antimony,bromine, iodine, a diazonium salt, hydrogen, or an alkyl group, and maybe the same or different. The first and second dopant species may differin concentration, attachment pattern to the graphene substrate, ornumber density.

Either or both dopant species may include a plurality of intermixeddopant subspecies, which may include the same or different subspecies,and which may differ in attachment pattern or relative concentrationfrom one another. One or more dopant subspecies may vary inconcentration within the first defined region. The first dopant speciesmay include a first bound moiety affixed to the graphene substrate and afirst free moiety removably attached to the first bound moiety, in whichcase the difference in the electronic property may be a function of aproperty of the free moiety. The second dopant species may include asecond bound moiety affixed to the graphene substrate and a second freemoiety removably attached to the second bound moiety, in which case thefirst and second bound moieties may be the same or different. The firstdopant species may be adsorbed onto the graphene substrate (e.g.,chemisorbed or physisorbed), chemically bound to the substrate (e.g.,covalently bound), or intercalated in the graphene substrate. The firstdopant species may vary in concentration or attachment pattern withinthe first defined region. The second defined region may surround thefirst defined region.

In another aspect, an electronic device includes a graphene substrateincluding a first defined region and a second defined region differingin at least one electronic property (e.g., Fermi level, band structure,carrier populations, mobility, tunneling behavior, or conductivecharacter) from the first defined region. The first region is chemicallyfunctionalized with a first dopant species and a second dopant specieson opposing surfaces of the graphene substrate.

The difference in the at least one electronic property may be aconsequence of the functionalization of the first and second definedregions. The first and second defined regions may form a semiconductingjunction, and may be parts of a component such as a diode, a transistor,a switch, a resistor, a capacitor, an inductor, a sensor, or aninterconnect. The device may further include a first interconnectelectrically connected to the first defined region and a secondinterconnect electrically connected to the second defined region. Thegraphene substrate may include a single layer or a multilayer. The firstdefined region and the second defined region may be adjacent, and eithermay not include an edge of the graphene substrate. The device mayfurther include a third defined region differing in at least oneelectronic property from each of the first defined region and the seconddefined region. The third defined region may be chemicallyfunctionalized with a third dopant species. The first or second dopantspecies may includes at least one of an amine, an imine, an organic freeradical, an aromatic molecule, nitrogen, boron, gold, bismuth, antimony,bromine, iodine, a diazonium salt, hydrogen, or an alkyl group, and maybe the same or different. The first and second dopant species may differin concentration, attachment pattern to the graphene substrate, ornumber density.

Either or both dopant species may include a plurality of intermixeddopant subspecies, which may include the same or different subspecies,and which may differ in attachment pattern or relative concentrationfrom one another. One or more dopant subspecies may vary inconcentration within the first defined region. The first dopant speciesmay include a first bound moiety affixed to the graphene substrate and afirst free moiety removably attached to the first bound moiety, in whichcase the difference in the electronic property may be a function of aproperty of the free moiety. The second dopant species may include asecond bound moiety affixed to the graphene substrate and a second freemoiety removably attached to the second bound moiety, in which case thefirst and second bound moieties may be the same or different. The firstdopant species may be adsorbed onto the graphene substrate (e.g.,chemisorbed or physisorbed), chemically bound to the substrate (e.g.,covalently bound), or intercalated in the graphene substrate. The firstdopant species may vary in concentration or attachment pattern withinthe first defined region. The second defined region may surround thefirst defined region.

In another aspect, a method of forming an electronic device on agraphene substrate includes functionalizing a first defined region ofthe graphene substrate with a first dopant species on a first side ofthe graphene substrate, and functionalizing a second defined region ofthe graphene substrate with a second dopant species on an opposingsecond side of the graphene substrate. The first defined region and thesecond defined region differ in at least one electronic property (e.g.,Fermi level, band structure, carrier populations, mobility, tunnelingbehavior, or conductive character).

Functionalizing the first or second defined region may includeselectively exposing the first defined region to a chemical solution,lithographically masking the graphene substrate, applying a spatiallypatterned electrical potential to the graphene substrate, or introducinga defect into the graphene substrate. The first defined region and thesecond defined region may be functionalized simultaneously orsequentially. The second defined region may overlap the first definedregion. Either or both of the dopant species may exclude the other fromdepositing on the graphene substrate. The second defined region maysurround the first defined region, or the first defined region maysurround the second defined region.

In another aspect, a method of making an electronic device includesapplying a first functional group to a graphene substrate in a firstpredetermined pattern, and applying a second functional group in asecond predetermined pattern to the graphene substrate patterned withthe first functional group. The second predetermined pattern is at leastpartially determined by the application of the first functional group.

The method may further include removing at least a portion of the firstfunctional group from the graphene substrate subsequent to applying thesecond functional group. The first or second predetermined pattern maybe aligned in a predetermined relationship to a crystal direction of thegraphene substrate. Applying the first functional group may includeselectively exposing the first defined region to a chemical solution,lithographically masking the graphene substrate, applying a spatiallypatterned electrical potential to the graphene substrate, or introducinga defect into the graphene substrate. Either or both of the functionalgroups may exclude the other from depositing on the graphene substrate.

In another aspect, a method of making an electronic device includesapplying a first functional group to a graphene substrate, and applyinga second functional group to the first functional group in apredetermined pattern.

The second functional group may bonds to or exchange with the firstfunctional group. After application of the second functional group, thegraphene substrate may include a first region and a second regiondiffering in at least one electrical property (e.g., Fermi level, bandstructure, carrier populations, mobility, tunneling behavior, orconductive character). The predetermined pattern may be aligned in apredetermined relationship to a crystal direction of the graphenesubstrate. Applying the first functional group may include selectivelyexposing the first defined region to a chemical solution,lithographically masking the graphene substrate, applying a spatiallypatterned electrical potential to the graphene substrate, or introducinga defect into the graphene substrate. Either or both of the functionalgroups may exclude the other from depositing on the graphene substrate.

In another aspect, an electronic device includes a graphene substrateincluding a first defined region and a second defined region differingin at least one electronic property (e.g., Fermi level, band structure,carrier populations, mobility, tunneling behavior, or conductivecharacter) from the first defined region. The first region is chemicallyfunctionalized with a first dopant species and the second defined regionis chemically functionalized with a second dopant species, and the firstdefined region has a border aligned with a crystal direction of thegraphene substrate.

The difference in, the at least one electronic property may be aconsequence of the functionalization. The first and second definedregions may form a semiconducting junction, and may be parts of acomponent such as a diode, a transistor, a switch, a resistor, acapacitor, an inductor, a sensor, or an interconnect. The device mayfurther include interconnects electrically connected to the first andsecond defined regions. The graphene substrate may include a singlelayer or a multilayer. The first and second regions may be adjacent, andeither or both may be remote from an edge of the graphene substrate. Thedevice may further include a third defined region differing in at leastone electronic property from the first and second defined regions, whichmay be functionalized with a third dopant species. The graphenesubstrate may be disposed on a base substrate (e.g., graphite or acrystal containing a noncarbon component). The first and second dopantspecies may functionalize a common surface of the substrate or opposingsurfaces, and either or both may include an amine, an imine, an organicfree radical, an aromatic molecule, nitrogen, boron, gold, bismuth,antimony, bromine, iodine, a diazonium salt, hydrogen, or an alkylgroup, and may be different or the same. The first and second dopantspecies may differ in concentration, attachment pattern to the graphenesubstrate, or number density.

Either or both dopant species may include a plurality of intermixeddopant subspecies, which may include the same or different subspecies,and which may differ in attachment pattern or relative concentrationfrom one another. One or more dopant subspecies may vary inconcentration within the first defined region. The first dopant speciesmay include a first bound moiety affixed to the graphene substrate and afirst free moiety removably attached to the first bound moiety, in whichcase the difference in the electronic property may be a function of aproperty of the free moiety. The second dopant species may include asecond bound moiety affixed to the graphene substrate and a second freemoiety removably attached to the second bound moiety, in which case thefirst and second bound moieties may be the same or different. The firstdopant species may be adsorbed onto the graphene substrate (e.g.,chemisorbed or physisorbed), chemically bound to the substrate (e.g.,covalently bound), or intercalated in the graphene substrate. The firstdopant species may vary in concentration or attachment pattern withinthe first defined region. The second defined region may surround thefirst defined region, or the first defined region may surround thesecond defined region.

In another aspect, an electronic device includes a graphene substrateincluding a first defined region and a second defined region differingin at least one electronic property (e.g., Fermi level, band structure,carrier populations, mobility, tunneling behavior, or conductivecharacter) from the first defined region. The first region is chemicallyfunctionalized with a first dopant species, has a border aligned with acrystal direction of the graphene substrate, and is remote from any edgeof the graphene substrate.

The second defined region may be chemically functionalized with a seconddopant species, which may differ from the first dopant species. Thefirst and second dopant species may differ in concentration, attachmentpattern on the graphene substrate, or number density. Either or bothdopant species may include a plurality of intermixed dopant subspecies,which may include the same or different subspecies, and which may differin attachment pattern or relative concentration from one another. One ormore dopant subspecies may vary in concentration within the firstdefined region. The first and second dopant species may functionalize acommon surface of the substrate or opposing surfaces, and either or bothmay include an amine, an imine, an organic free radical, an aromaticmolecule, nitrogen, boron, gold, bismuth, antimony, bromine, iodine, adiazonium salt, hydrogen, or an alkyl group, and may be different or thesame.

The difference in the at least one electronic property may be aconsequence of the functionalization. The first and second definedregions may form a semiconducting junction, and may be parts of acomponent such as a diode, a transistor, a switch, a resistor, acapacitor, an inductor, a sensor, or an interconnect. The device mayfurther include interconnects electrically connected to the first andsecond defined regions. The graphene substrate may include a singlelayer or a multilayer. The first and second regions may be adjacent, andthe second region may be remote from an edge of the graphene substrate.The device may further include a third defined region differing in atleast one electronic property from the first and second defined regions,which may be functionalized with a third dopant species. The graphenesubstrate may be disposed on a base substrate (e.g., graphite or acrystal containing a noncarbon component). The first dopant species mayinclude a first bound moiety affixed to the graphene substrate and afirst free moiety removably attached to the first bound moiety, in whichcase the difference in the electronic property may be a function of aproperty of the free moiety. The second defined region may be chemicallyfunctionalized with a second dopant species including a second boundmoiety affixed to the graphene substrate and a second free moietyremovably attached to the second bound moiety, in which case thecomposition of the first and second bound moieties may be the same ordifferent. The first dopant species may be adsorbed onto the graphenesubstrate (e.g., chemisorbed or physisorbed), chemically bound to thesubstrate (e.g., covalently bound), or intercalated in the graphenesubstrate. The first dopant species may vary in concentration orattachment pattern within the first defined region. The second definedregion may surround the first defined region, or the first definedregion may surround the second defined region.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic of a graphene-based electronic device.

FIG. 2 is a schematic of a graphene-based capacitor.

FIG. 3 is a flow chart describing a process for forming a graphene-basedelectronic device.

FIG. 4 is a schematic of a two-sided graphene-based device.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here.

Graphene, a freestanding monolayer of graphite, exhibits uniqueelectronic properties, including very high conductivity and unusualquantum effects (e.g., zero effective mass charge carriers with lowscattering). Graphene sheets may be manufactured by flaking off ofgraphite (e.g., highly oriented pyrolytic graphite (HOPG)), by growingas an epitaxial layer on other crystals and chemically etching to removethe graphene, or by reducing graphite oxide. See, e.g., Li, et al.,“Large-area synthesis of high-quality and uniform graphene films oncopper foils,” Science 324:1312-1314 (2009); Geim, et al., “The rise ofgraphene,” Nature Mat'ls 6:183-191 (March 2007); Benayad, et al.,“Controlling work function of reduced graphite oxide with Au-ionconcentration,” Chem Phys Lett, 475: 91-95 (2009), each of which isincorporated by reference herein. Either before or after removal fromthe graphite or heterogeneous substrate, graphene may be chemicallyfunctionalized to produce electronic devices. While the description thatfollows focuses on monolayer graphene, chemical functionalization ofoligolayers may also yield interesting electronic properties.

FIG. 1 is a schematic of a graphene-based electronic device. In theillustrated embodiment, graphene sheet 10 includes three doped regions12, 14, 16. Region 12 is functionalized with a species that renders itn-type relative to pristine (pure) graphene. Region 14 is functionalizedwith a species that renders it p-type relative to pristine graphene, andregion 16 is functionalized with a species that renders it moreinsulating than pristine graphene. Regions 18 may be undoped,functionalized with a conductive species, or functionalized with aspecies that renders the underlying graphene more conductive than region16, to form interconnects. In the illustrated embodiment, the devicefunctions as a simple p-n junction diode. By analogy with silicon-basedsemiconducting devices, other arrangements of p-type and n-type regionsmay be used to construct transistors, switches, and other electroniccomponents. Further, dopant species and/or concentrations may be variedin some regions to produce other components, such as resistors,capacitors, inductors, sensors, or interconnects. For example, FIG. 2illustrates a graphene-based capacitor. Interdigitated conductiveregions 30 and 32 are separated by dielectric region 34 in atwo-dimensional analog of a typical capacitor design. In otherembodiments, conductive regions may form opposing T-shapes or doublespirals, for example. A spiral configuration may also be used to form aninductor, for example.

A method of forming a device like that in FIG. 1 is illustrated in FIG.3. In the illustrated embodiment, a pure graphene sheet is masked (usingconventional lithographic methods) to expose only region 12, which isthen exposed to a chemical that forms an n-type region. For example,exposure of graphene to NH₃ gas at elevated temperatures will tend toform an n-type region by covalent bonding, particularly at edges anddefect sites, as described in Wan, et al., Science 324(5928):768-771(May 2009), which is incorporated by reference herein. N-doped graphenemay also be formed by chemical vapor deposition of a mixture of NH₃ andCH₄ gas, or by arc discharge of carbon electrodes in the presence ofH₂/pyridine or H₂/NH₃. See, e.g., Wei, et al., “Synthesis of N-DopedGraphene by Chemical Vapor Deposition and Its Electrical Properties,”Nano Lett. 9(5):1752-1758 (2009); Panchakarla, et al., “Synthesis,Structure, and Properties of Boron and Nitrogen Doped Graphene,” Adv.Mat., 21(46):4726-4730 (August 2009), each of which are incorporated byreference herein. Other suitable electron-donating agents which may beadsorbed onto the graphene surface include organic free radicals (e.g.,4-amino-TEMPO), aromatic molecules with electron-donating groups, orelectron-donating macromolecules such as poly(ethylene imine). See,e.g., Choi, et al., “Chemical Doping of Epitaxial Graphene by OrganicFree Radicals,” J. Phys. Chem. Lett. 2010(1):505-509 (2010); Dong, etal., “Doping Single-Layer Graphene with Aromatic Molecules,” Small5(12):1422-1426 (June 2009); Farmer, et al., “Chemical Doping andElectron-Hole Conduction Asymmetry in Graphene Devices,” Nano Lett.,9(1):388-392 (2009), each of which are incorporated by reference herein.In the illustrated embodiment, the region 12 is remote from any edge ofthe graphene sheet (i.e., far enough away from the edge that electricalproperties imparted by the donor species are no more than minimallyaffected by the existence of the edge). In some embodiments, the bordersof region 12 may be aligned with a crystal direction of the graphene,while in other embodiments, the borders may be at any angle to thecrystal axis. In some embodiments, application of the functional groupmay include applying an electric potential to the graphene substrate,e.g., a patterned electric potential.

In an embodiment, it may be desirable to introduce one or more defectsinto the region before exposure to NH₃ (or other dopants), which isbelieved to be chemically reactive at defect sites. For example, afocused electron beam may be used to introduce one or more defects intothe graphene lattice at region 12 before exposure, or the masked regionmay be exposed to an oxygen plasma. (In an embodiment, simultaneousn-doping and reduction of oxidized graphene may be achieved by exposureto an oxygen plasma. See, e.g., Li et al., “Simultaneous Nitrogen-Dopingand Reduction of Graphene Oxide,” J. Am. Chem. Soc., 131(43):15939-15944(2009), which is incorporated by reference herein.) Very preciselyplaced defect sites may also be introduced by use of an atomic forcemicroscope. In an embodiment, with sufficiently well-controlledintroduction of defects and chemical functionalization, it may bepossible to eliminate the need to mask the region, defining the dopedregion by selective introduction of defects into the graphene lattice.In an embodiment, it may be possible to anneal or otherwise heal suchdefects after doping.

Once region 12 has been formed, the substrate may be cleaned andremasked according to standard lithographic techniques, then exposed toa different electron donor species to form p-type region 14. Forexample, substitution of boron into the graphene backbone will tend toform a p-type region, as will adsorption (or intercalation in grapheneoligolayers) of bromine, iodine, aromatic structures includingelectron-withdrawing groups, or diazonium salts (e.g., 4-bromobenzenediazonium tetrafluorate), or deposition of gold, bismuth, or antimony(in some embodiments, followed by annealing). See, e.g., Panchakarla, etal., “Synthesis, Structure, and Properties of Boron and Nitrogen DopedGraphene,” Adv. Mat., 21(46):4726-4730 (August 2009); Jung, et al.,“Charge Transfer Chemical Doping of Few Layer Graphenes: ChargeDistribution and Band Gap Formation,” Nano Lett., 9(12):4133-4137(2009); Dong, et al., “Doping Single-Layer Graphene with AromaticMolecules,” Small 5(12):1422-1426 (June 2009); Fanner, et al., “ChemicalDoping and Electron-Hole Conduction Asymmetry in Graphene Devices,” NanoLett., 9(1):388-392 (2009); Gierz, et al., “Atomic Hole Doping ofGraphene,” Nano Lett. 8(12):4603-4607 (2008), each of which areincorporated by reference herein. For any of these species, in someembodiments, it may be preferable to introduce defects into the grapheneas described above.

Once region 14 has been formed, the substrate may be cleaned andremasked, then exposed to a different to form region 16. For example,exposure of graphene to atomic hydrogen (e.g., as a plasma) will tend toform an insulating region (“graphane”). (P-type regions may also beproduced by annealing of graphane regions formed by exposure to hydrogenplasma.) See, e.g., Elias, et al., “Control of Graphene's Properties byReversible Hydrogenation: Evidence for Graphane,” Science 323:610-613(2009), which is incorporated herein by reference. In general, selectiverehybridization of graphene's carbon atoms from an sp² state to an sp³state will tend to open a band gap, thus producing semiconducting orinsulating regions. For example, alkylation or arylation may alsoproduce semiconducting or insulating regions. Optionally, afterformation of region 16, regions 18 may also be formed by lithographicmethods. Alternatively, regions 18 may consist essentially of pristinegraphene. It will be understood that the steps of forming the differentregions may occur in any convenient order. For example, if theconditions required to produce an n-type region might tend to degrade ap-type region on the same sheet, then it may be preferable to firmproduce the n-type region(s), and follow with production of the p-typeregion(s).

One challenge in nanolithography is registration when successive masksare used on the same substrate. In an embodiment, registration “marks”may be placed on the graphene substrate in the form of easily detectablefunctional groups (which may or may not have any function in a finalelectronic device). For example, electroluminescent polymers (e.g.,oligomers) such as poly(p-phenylene vinylene) may be well suited to beused as markers, forming large, rigid structures which may be detectedby their photon emission. In an embodiment, X-ray emitters may be placedon the substrate, but caution is needed to avoid degradation of thefinal product by the emitted X-rays.

In an embodiment, rather than individually functionalizing each regionof a graphene sheet with a different dopant species as described above,it may be desirable to functionalize the entire sheet (or a portion ofthe sheet) with a species, and then to lithographically create thedesired regions, either by swapping the whole functional molecule, or byadding new functionality (as a free moiety attached to a bound moietyaffixed to the substrate) that confers the desired properties. In anembodiment, graphene circuits may be made partially or fully rewritableby such methods. For example, carbon nanofibers have been modified withelectrochemically active ferrocene groups by the Cu(I)-catalyzedazide-alkyne cycloaddition reaction (“click” chemistry). See, e.g.,Landis, et al., “Covalent grafting of redox-active molecules tovertically aligned carbon nanofiber arrays via ‘click’ chemistry,” Chem.Mater., 21(4):724-730 (2009), which is incorporated by reference herein.This approach is expected to be applicable to modification of graphenefunctionalized with azide, as well. In an embodiment, functional groupsmay be adsorbed (e.g., physisorbed or chemisorbed) onto the graphenesurface, rather than covalently bonded. Some dopant species may alsointercalate in oligolayers of the graphene substrate.

While the above methods have been described in connection withproduction of a single p-n junction surrounded by an insulator, morecomplicated geometries, for example including many interconnecteddevices, may be produced by following the same steps, for example byusing masks that include a plurality of openings to form many regionshaving each desired carrier density. In general, most anytwo-dimensional arrangement of doped regions for silicon devices isexpected to have a graphene analog.

Further, the above methods are described with reference to deposition ofa single dopant species in each region. In some embodiments, multipledopant species may be applied to a single region. These may co-deposit(in a spontaneously ordered, partially ordered, or randomconfiguration), or the deposition of one species may exclude the bondingof another to the graphene surface. In the latter case, the exclusioneffect may be used to improve registration of multiple regions. Forexample, if an electron donor dopant species also has the property ofexcluding an electron acceptor dopant species, then p-type region 14might be produced first. Subsequent masking to produce region 12 wouldnot need to be precisely aligned at the border between regions 12 and14, but could form some degree of overlap, and the exclusion of theacceptor species would produce two adjacent but not overlapping regions.

Certain species are known to deposit on graphene in ordered patternsthat depend on the character of their bond with carbon and also onsteric considerations. These effects may be used in sequential reactionsto deposit other species in an ordered fashion at less than fullsaturation. For example, it has been calculated that optimum coverage ofphenyl groups on graphene is at 2 phenyl groups per unit cell of 18graphene carbon atoms, for a coverage density of 11%. See, e.g.,Bekyarova et al., Phys. Status Solidi RRL, 3(6):187-189 (2009), which isincorporated by reference herein. A graphene substrate may be coveredwith phenyl groups at this density, and then subsequently exposed to aphysically smaller dopant species (e.g., a metal or a halide), which isexpected to deposit in between the phenyl groups. Finally, the phenylgroups may optionally be removed, leaving behind the smaller dopantspecies at a less than fully saturated concentration. In an embodiment,the phenyl groups may be adsorbed, rather than covalently bonded to thegraphene, to facilitate removal. More complicated multistep processesfor doping may also be envisioned, for example following the removal ofthe phenyl groups with doping with another small dopant species thatdoes not displace the first non-saturated small dopant species, therebyachieving a patterned co-deposited layer. These techniques may also beused, for example to produce a graphene substrate including two dopedregions which are each doped with the same intermixed co-dopants, but indifferent concentrations, number density, or attachment pattern. Dopantsmay also be deposited in a gradient concentration across a region, arandom concentration, or in any other suitable pattern in whichconcentration varies with in a region. A mixture of dopants may also besimultaneously co-deposited in a single region, in which case thedopants may deposit randomly, in a partially ordered fashion, or in afully ordered fashion (e.g., by spontaneous self assembly into anordered array).

In an embodiment, one or both sides of a free graphene sheet may befunctionalized. For example, in the embodiment shown in FIG. 4, region40 is functionalized with a first dopant species, and region 42 isfunctionalized with a second dopant species on the opposite side of thegraphene sheet. Region 44 represents an overlap area between thefunctionalized regions which is expected to have different electronicproperties than either of the non-overlapping functionalized regions.

In an embodiment, instead of or in addition to lithographic masking ofthe substrate, deposition may be controlled by applying a patternedelectric or magnetic field in the vicinity of the substrate.

In one example, a p-n junction in the configuration of FIG. 1 is formedas follows. A pristine graphene substrate is formed by flaking fromHOPG. The substrate is masked with a lithographic mask exposing region16 and exposed to a cold hydrogen plasma (0.1 mbar 10% hydrogen-90%argon mixture at 30 cm for 2 hr) to form graphane in the region. (See,Elias, et al., supra.) The mask is then removed.

The substrate is masked with a water- and alcohol-compatiblelithographic mask that exposes region 14, and then immersed in a 1 mMsolution of 4-bromobenzenediazonium tetrofluoroborate in a 1:1water/methanol mixture at 300 K for 2 h and rinsed with water andmethanol, thereby doping the region with diazonium to produce a p-typeregion. (See Farmer et al., supra.) The lithographic mask is thenremoved.

Finally, the substrate is then masked with a lithographic mask thatexposes regions 12 and 14. The surface is dosed using a direct doser(controlled by means of a variable leak valve) with azidotrimethylsilane(ATS), which adsorbs via nitrene radical onto the graphene surface. (SeeChoi et al., supra.) The already-doped region 14 excludes the ATS, soonly region 12 is doped to produce an n-type region. The mask is thenremoved. Regions 18 have not been exposed to any of thegraphene-modifying procedures in this example, and thus remain pristinemetallic or semiconducting graphene.

In another example, an epitaxially grown graphene layer on anitrogen-doped SiC substrate has an intrinsic n-type character. Thegraphene is masked to expose region 14 and gold is deposited using aKnudsen cell at room temperature. The substrate is then annealed at 700°C. for 5 min, which simultaneously allows the gold to bond to thegraphene layer (forming a p-type region) and decomposes the resist.(See, Gierz et al., supra.) The layer is then remasked to cover regions12 and 14 and expose region 16 and exposed to a solution of4-nitrophenyl diazonium tetrofluoroborate, which forms an insulatingregion. (See Bekyarova et al., supra.) The resist is then removed,leaving a p-n junction surrounded by an insulating region.

In an embodiment, dopants may be selected to adjust other electronicproperties of graphene besides the carrier populations described above,such as Fermi level, band structure, mobility, tunneling behavior, orconductive character. For example, effects of adsorbates on Fermi leveland Fermi velocity are discussed in Khomyakov, et al., “First-principlesstudy of the interaction and charge transfer between graphene andmetals,” Phys Rev B, 79:195425 (2009); Giovannetti, et al., “Dopinggraphene with metal contacts,” Phys Rev Lett, 101:026803 (2008);Benayad, et al., “Controlling work function of reduced graphite oxidewith Au-ion concentration,” Chem Phys Lett, 475:91-95 (2008); andTapaszto, et al., “Tuning the electronic structure of graphene by ionirradiation,” Phys Rev B, 78:233407 (2008), each of which isincorporated by reference herein.

In an embodiment, rather than or in addition to adjusting charge carrierpopulations as discussed above, dopant species may be selected to modifyoptical or electro-optical properties of graphene, such as optical gain,transmissivity, reflectivity, permittivity, permeability, refractiveindex, or anisotropy, for example to form plasmonic devices (lasing orpassive) or other nonlinear electro-optical devices. Pristine grapheneis found to absorb to πα=2.3% of incident white light despite having athickness of one atom (where α is the fine structure constant,approximately 1/137). Disruption of the graphene's sp² network (e.g., bysp³ bond formation) reduces the transparency as observed in grapheneoxide. See, e.g., Nair, et al., “Fine structure constant defines visualtransparency of graphene,” Science, 320:1308 (2008); Kim, et al.,“Large-scale pattern growth of graphene films for stretchabletransparent electrodes,” Nature, 457:706-710 (2009); U.S. PublishedApplication No. 2009/0146111 to Shin et al.; Rao, et al., “Some novelattributes of graphene.”J Phys Chem Lett; 1:572-580 (2010), each ofwhich is incorporated by reference herein. Those of skill in the artwill recognize how to use these optical or electro-optical properties toconstruct various graphene-based optoelectronic devices by analogy withsilicon-based or other known devices, such as lasers, light-emittingdiodes, plasmon waveguides, optical waveguides, optical gratings,fluorescent devices, light-absorbing devices, photoelectron converters,phaseshifting devices, interferometers, optical couplers, or plasmoncouplers.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the artbased on the teachings herein. The various aspects and embodimentsdisclosed herein are for purposes of illustration and are not intendedto be limiting, with the true scope and spirit being indicated by thefollowing claims.

While particular aspects of the present subject matter described hereinhave been shown and described, it will be apparent to those skilled inthe art that, based upon the teachings herein, changes and modificationsmay be made without departing from this subject matter described hereinand its broader aspects and, therefore, the appended claims are toencompass within their scope all such changes and modifications as arewithin the true spirit and scope of this subject matter describedherein.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

It will be understood that, in general, terms used herein, andespecially in the appended claims, are generally intended as “open”terms (e.g., the term “including” should be interpreted as “includingbut not limited to,” the term “having” should be interpreted as “havingat least,” the term “includes” should be interpreted as “includes but isnot limited to,” etc.). It will be further understood that if a specificnumber of an introduced claim recitation is intended, such an intentwill be explicitly recited in the claim, and in the absence of suchrecitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage ofintroductory phrases such as “at least one” or “one or more” tointroduce claim recitations. However, the use of such phrases should notbe construed to imply that the introduction of a claim recitation by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a functional group” should typically be interpreted to mean“at least one functional group”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, it will be recognized that such recitation should typically beinterpreted to mean at least the recited number (e.g., the barerecitation of “two functional groups,” or “a plurality of functionalgroups,” without other modifiers, typically means at least twofunctional groups). Furthermore, in those instances where a phrase suchas “at least one of A, B, and C,” “at least one of A, B, or C,” or “an[item] selected from the group consisting of A, B, and C,” is used, ingeneral such a construction is intended to be disjunctive (e.g., any ofthese phrases would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, or A, B, and C together, and may further include more than oneof A, B, or C, such as A₁, A₂, and C together, A, B₁, B₂, C₁, and C₂together, or B₁ and B₂ together). It will be further understood thatvirtually any disjunctive word or phrase presenting two or morealternative terms, whether in the description, claims, or drawings,should be understood to contemplate the possibilities of including oneof the terms, either of the terms, or both terms. For example, thephrase “A or B” will be understood to include the possibilities of “A”or “B” or “A and B.” Moreover, “can” and “optionally” and otherpermissive terms are used herein for describing optional features ofvarious embodiments. These terms likewise describe selectable orconfigurable features generally, unless the context dictates otherwise.

The herein described aspects depict different components containedwithin, or connected with, different other components. It is to beunderstood that such depicted architectures are merely exemplary, andthat in fact many other architectures can be implemented which achievethe same functionality. In a conceptual sense, any arrangement ofcomponents to achieve the same functionality is effectively “associated”such that the desired functionality is achieved. Hence, any twocomponents herein combined to achieve a particular functionality can beseen as “associated with” each other such that the desired functionalityis achieved, irrespective of architectures or intermedial components.Likewise, any two components so associated can also be viewed as being“operably connected,” or “operably coupled,” to each other to achievethe desired functionality. Any two components capable of being soassociated can also be viewed as being “operably coupleable” to eachother to achieve the desired functionality. Specific examples ofoperably coupleable include but are not limited to physically mateableor interacting components or wirelessly interacting components.

1. A method of making an electronic device, comprising: applying a firstdopant species functional group to a graphene substrate in a firstpredetermined pattern to form a first doped region of the electronicdevice; and applying a second dopant species functional group in asecond predetermined pattern to the graphene substrate patterned withthe first dopant species functional group to form a second doped regionof the electronic device, wherein the second predetermined pattern is atleast partially determined by the application of the first dopantspecies functional group.
 2. The method of claim 1, further comprisingremoving at least a portion of the first dopant species functional groupfrom the graphene substrate subsequent to applying the second dopantspecies functional group.
 3. The method of claim 1, wherein the firstpredetermined pattern is aligned in a predetermined relationship to acrystal direction of the graphene substrate.
 4. The method of claim 3,wherein the second predetermined pattern is aligned in a predeterminedrelationship to a crystal direction of the graphene substrate.
 5. Themethod of claim 1, wherein applying the first dopant species functionalgroup includes selectively exposing the substrate to a chemicalsolution.
 6. The method of claim 1, wherein applying the first dopantspecies functional group includes lithographically masking the graphenesubstrate.
 7. The method of claim 1, wherein applying the first dopantspecies functional group includes applying a spatially patternedelectrical potential to the graphene substrate.
 8. The method of claim1, wherein applying the first dopant species functional group includesintroducing a defect into the graphene substrate.
 9. The method of claim1, wherein the first dopant species functional group at least partiallyexcludes the second dopant species functional group from depositing onthe graphene substrate.
 10. A method of making an electronic device,comprising: applying a first dopant species functional group to dope agraphene substrate; and applying a second dopant species functionalgroup to the first dopant species functional group in a predeterminedpattern to define a doping region in the graphene substrate for theelectronic device.
 11. The method of claim 10, wherein the second dopantspecies functional group bonds to the first dopant species functionalgroup.
 12. The method of claim 10, wherein the second dopant speciesfunctional group exchanges with the first dopant species functionalgroup.
 13. The method of claim 10, wherein after application of thesecond dopant species functional group, the graphene substrate includesa first region and a second region differing in at least one electricalproperty.
 14. The method of claim 10, wherein the predetermined patternis aligned in a predetermined relationship to a crystal direction of thegraphene substrate.
 15. The method of claim 10, wherein applying thefirst dopant species functional group includes selectively exposing thesubstrate to a chemical solution.
 16. The method of claim 10, whereinapplying the first dopant species functional group includeslithographically masking the graphene substrate.
 17. The method of claim10, wherein applying the first dopant species functional group includesapplying a spatially patterned electrical potential to the graphenesubstrate.
 18. The method of claim 10, wherein applying the first dopantspecies functional group includes introducing a defect into the graphenesubstrate.
 19. The method of claim 10, wherein the first dopant speciesfunctional group at least partially excludes the second dopant speciesfunctional group from depositing on the graphene substrate.